The present invention relates to a device for measuring vibrations on a rotating blade to determine or grasp level of vibrations on a rotating blade during an operation of a gas turbine or the like.
Hitherto, vibrations on a rotating blade of a turbine or the like during its operation have been measured such that signals based on vibrations of a rotating blade are detected with a strain gauge attached to the blade itself, which are transmitted to stationary parts by transmission means such as a slip ring, a rotary transformer and a microtransmitter, thereby displaying or recording the signals.
A strain gauge has, however, an upper limit of its operating temperature at approximately 800.degree. C., so that it cannot be used for measuring vibrations on a rotating blade of a gas turbine or the like whose temperature may reach a level as high as 1,300.degree. C.
Even in a steam turbine or the like where a strain gauge can be used because of the turbine temperature being below the upper limit of the operating temperature of the gauge, installation of the signal transmitting means will require considerable reconstruction of stationary and rotating parts of the turbine and attachment of the strain gauge on the rotating blade will cause changes in aerodynamic and vibration characteristics of the rotating blade, resulting in difficulty in accurate measurement of inherent vibration characteristics of the rotating blade itself.
The present invention was made to overcome the above disadvantages of the prior art and provides an improved device which uses no strain gauge to be attached on the rotating blade and is capable of optically measuring vibrations of a rotating blade operating at a high temperature without causing any change in the vibration characteristics of the blade.
Now, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.